A. Technical Field
The present invention relates to a column treating process and an apparatus therefor. More particularly, a subject of the present invention is a column treating process by a distillation column and so on, that is utilized when producing various chemical products and comprises: carrying out physical treatment such as isolation of a treating fluid component or chemical treatment such as reaction, of a treating fluid introduced in a column-shaped treating space, namely a treatment column; and taking out a formed desired product from a column top side by methods such as liquefying after evaporating once.
B. Background Art
In production processes for various chemical products, a column treating process by use of column apparatuses such as a distillation column, an absorption column and a stripping column is generally adopted industrially.
In the column treating process, with a liquid or gas treating fluid introducing to a treatment column, a desired physical or chemical treatment is carried out by heating or stirring the treating fluid in the treatment column, or affecting a fluid component supplied separately; a portion of a fluid after the treatment is moved to an upper portion of the column, namely a top column side, recovered by liquefying at the column top and taken out from the column top side. As the result, the mass above treating work can be carried out continuously and stably.
In the column treating process like this, accompanied by carrying out the treatment of the introduced treating liquid, except for a desired product, impurities may be formed by denaturing or polymerizing a component in the treating fluid. The formed impurities like this may stay or accumulate in the treating fluid without taking out as a desired product. In addition, impurities initially included in the treating fluid that is introduced to the treatment column also stay or accumulate in the treatment column. These impurities are usually apt to collect at the column bottom of the treatment column.
The impurities staying and accumulating in the treating fluid cause problems of: lowering heat-transfer characteristics of the treatment column by precipitating the impurities as a solid product and attaching to inner wall of the treatment column; packing various pipings, machines and so on; contaminating a desired product with a portion of the impurities; and lowering quality and capacity of the chemical treatment that carries out a treating solution.
The problem is illustrated by a concrete example. (Meth)acrylic acid and esters thereof are purified by use of a distillation apparatus comprising a distillation column, a heat exchanger and pipings in connection with both.
In this distilling treatment, polymers formed in the distillation column and are attached to inner wall of the distillation column because (meth)acrylic acid and esters thereof are polymerized easily. If the attached polymers accumulate, situations such as stopping the distillation column also arise. It is necessary to remove polymers attached to inner wall by breaking up the distillation column regularly in order to maintain treating quality of the distillation column and to operate stably. Therefore, it takes much labor and productivity is caused to lower greatly.
As a method to solve this problem, a method that comprises introducing oxygen gas from the column bottom for prevention of polymerization in the distillation column is disclosed in JP-B-34606/1977 and JP-B-61015/1982. A method that comprises taking out streamed solution falling in a rectifying column, separating a polymer in the solution, and circulating the polymer into the rectifying column again is disclosed in JP-A-239341/1996.
Neither the above prior art method that comprises introducing oxygen gas nor the above prior art method that comprises separating a polymer from a fallen reflux solution can remove impurities such as a polymer accumulated in a treating solution enough.
Though a problem such as stopping a distillation column or a rectifying column is not caused for a short time operation, polymers are gradually produced and attached to: an drawing out pipe for a column bottom solution, a forwarding pump for a column bottom solution, a pipe that columns such as a reboiler comprise, a heat exchanger and inner portions of a pipe for a long time operation, and it becomes impossible to continue distilling because of causing to block soon. Except for the polymers produced during the treatment, precipitates such as aforementioned impurities contained in the treating solution and denatured products produced during the treatment, can cause the same problem. Further precipitation and polymerization are increased by attaching these polymers and precipitates in the pipes and machines.
In addition, it can be considered to prevent the impurities from intruding into a treatment column by filtrating a treating solution before introducing into the treatment column. However this method is not effective for impurities that are produced in the treatment column. Methods of hindering the impurities from being forwarded into a treating apparatus of the next step or preventing the impurities from attaching to pipes toward the next step can be considered by filtrating the whole of the column bottom drawn solution and thereafter forwarding the solution to the next step. However it is not useful to prevent the impurities from attaching in the treatment column, and it is difficult to effectively filtrate the column bottom drawn solution that contains plenty of impurities.
These prior treating methods cannot prevent solid products from attaching in the pipes and machines enough.
A. Object of the Invention
An object of the present invention is to provide a column treating method by use of the aforementioned distillation column and so on, which method enables to effectively remove solid impurities such as precipitates and polymers contained or produced in a treating fluid, and to thereby stably operate the column treatment.
B. Disclosure of the Invention
A column treating process, according to the present invention, comprises: introducing a treating fluid in a treatment column, carrying out physical and/or chemical treatment of the treating fluid in the treatment column, taking out a portion of a fluid after the treatment from a column top side, and drawing out a residual fluid that is not taken out from the column top side but is left from a column bottom side. And with advancing the treatment in the treatment column, the process further comprises performing continuously:
step (a): drawing out the treating fluid from the column bottom side outside the treatment column,
step (b) of removing solid impurities from the treating fluid drawn out in step (a), and
step (c) of returning the treating fluid, from which the solid impurities are removed in step (b), to the treatment column.
A column treating apparatus, according to the present invention, which carries out the column treating process and comprises:
a treatment column, in order to carry out the treatment of the treating fluid in the treatment column,
an introducing inlet, placed in the treatment column in order to introduce the treating fluid,
a taking out outlet, placed on the column top side of the treatment column in order to take out a portion of the fluid after the treatment,
a treating fluid circulating route, placed on the column bottom side of the treatment column in order to draw out the treating fluid in the treatment column outside the treatment column and to return the treating fluid again to the treatment column, and
an impurities-removing portion, placed in the circulating route in order to remove the solid impurities from the treating fluid.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.